Adding a test which check that a ServerConfigurationError is raised
when the file 'emailSettings.init' is missing in the server.

Now it fails because a ConfigParser exception is wrongly raised:
    ConfigParser.NoSectionError: No section: 'email'
that is confusing
fix: now raise SeverConfigurationError instead of ConfigParser.NoSectionError
if the email_settings.ini file is missing
removed 'os_path_exists' wrapper of os.path.exists; test rewritten
[test_server] use the 'mock' library to test the ServerConfigurationError exception in case of email settings file missing
Merge pull request #78 from iacopy/fix-no-section-email-exception

Fix no section email exception